In some cases, Firefox may not remember changes you've made to your toolbar settings or certain other configuration changes, such as window size or position. This article explains how to fix the underlying problem that may result in one or more of the following symptoms:

• You have customized your Firefox toolbar to add, rearrange or remove buttons but the changes are not saved when you restart Firefox.
• You have resized or moved the browser window, but the new size or position is not remembered when you restart Firefox.
• You cannot save new bookmarks.

Here are two ways that you can solve the problem:

Solution 1: Delete xulstore.json file

You may have a corrupt xulstore.json file in your Firefox profile. You can delete this file so that Firefox can create a new one.

1. • Click the menu button , click Help and select More Troubleshooting Information.From the Help menu, select More Troubleshooting Information. The Troubleshooting Information tab will open.
   • Under the Application Basics section next to Profile FolderProfile Directory, click Open FolderShow in FinderOpen Directory. A window will open that contains your profile folder.Your profile folder will open.Your profile directory will open.
   Note: If Firefox displays an error after clicking Open Folder or if you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.
2. Close Firefox: Click the Firefox menu and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu and select Quit.
3. Locate and delete the file xulstore.json (or rename it, for example, to xulstore.jsonOLD, to keep the old file as a backup).
4. You can close the profile folder and open Firefox now.

Solution 2: Refresh Firefox

If you don't want to try the first solution or if it didn't work, the Firefox refresh feature will automatically restore default toolbar settings and browser window size or position, and will also remove add-ons (extensions and themes) that could be interfering.

1. Click the menu button , click Help, and select More Troubleshooting Information.
2. Click Refresh Firefox… then Refresh Firefox in the confirmation window that opens. Firefox will close to refresh itself.
3. When finished, a window will list your imported information. Click the Finish button. Firefox will open.
4. Select whether you want Firefox to restore all or some windows and tabs, and click the Let's go! button.